Chiari Malformation is a structural defect that typically occurs during fetal development but may also occur due to drainage of excessive spinal fluid. Normally, the cerebellum lies above the opening to the skull (also known as the foramen magnum). With Chiari malformation, the cerebellum extends below the foramen magnum and into the spinal canal. There are four types of Chiari malformation with type 1 being the most prevalent.
A study of 73 patients with Chiari Malformation Type 1 (CM-1) 11% had chronic migraine, which is almost 3 times the rate in the general population.1